games.cavu.tier-madness.move

One secret move by a player, written (by the game server, on the player's behalf, or by the player) to the round's secret space (skey `{game}-r{round}`). Only the game server can read it until that round's reveal, when the game's players can too (round 0, the category vote, opens at game end). Its CID is published as a games.cavu.tier-madness.commitment (same rkey) in the game's commitment space, so the move can't be changed later. The nonce stops anyone from guessing a low-entropy move (e.g. a tier) by hashing every possibility.